package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Autowired
    private StringRedisTemplate stringRedisTemplate;
    @Autowired
    private CacheClient cacheClient;

    @Override
    public Result queryShopById(Long id) {
        // 解决缓存穿透
//        Shop shop = cacheClient.queryWithTrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);

        // 互斥锁解决缓存击穿
        // Shop shop = cacheClient
        //         .queryWithMutex(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);

        // 逻辑过期解决缓存击穿
         Shop shop = cacheClient.queryWithLogicalExpire(id,Shop.class,CACHE_SHOP_KEY,this::getById,20L,TimeUnit.SECONDS);
//                 .queryWithLogicalExpire(CACHE_SHOP_KEY, id, Shop.class, this::getById, 20L, TimeUnit.SECONDS);

        if (shop == null) {
            return Result.fail("店铺不存在！");
        }
        // 7.返回
        return Result.ok(shop);
        /*
        解决缓存击穿问题
         */
//        Shop shop = queryWithMutex(id);
      //解决缓存穿透问题
//        shop = queryWithTrough(id);
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if(id==null){
            return Result.fail("店铺id不能为空");
        }
        //更新数据库
        updateById(shop);
        //2、删除缓存
        stringRedisTemplate.delete("cache:shop:"+id);
        return Result.ok();
    }
    /*
        尝试获取锁
     */
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    /*
    释放锁
     */
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
    public void ShopSaveRedis(Long id,Long expireSeconds){
        //1、查询店铺数据
        Shop shop = getById(id);

        //2、封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //3、写如Redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY+id, JSONUtil.toJsonStr(redisData));
    }
    public Shop queryWithMutex(Long id)  {
        String key = CACHE_SHOP_KEY + id;
        // 1、从redis中查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get("key");
        // 2、判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            // 存在,直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //判断命中的值是否是空值
        if (shopJson != null) {
            //返回一个错误信息
            return null;
        }
        // 4.实现缓存重构
        //4.1 获取互斥锁
        String lockKey = "lock:shop:" + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            // 4.2 判断否获取成功
            if(!isLock){
                //4.3 失败，则休眠重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            //4.4 成功，根据id查询数据库
            shop = getById(id);
            // 5.不存在，返回错误
            if(shop == null){
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL,TimeUnit.MINUTES);
                //返回错误信息
                return null;
            }
            //6.写入redis
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_NULL_TTL,TimeUnit.MINUTES);

        }catch (Exception e){
            throw new RuntimeException(e);
        }
        finally {
            //7.释放互斥锁
            unlock(lockKey);
        }
        return shop;
    }
    /*
    缓存穿透
     */
    public Shop queryWithTrough(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1、从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        if(StrUtil.isNotBlank(shopJson)){
            //存在直接返回,toBean转化为Shop.class对象
            Shop shop = JSONUtil.toBean(shopJson,Shop.class);
            return shop;
        }
        //判断shop是否为空
        if(shopJson==null){
            return null;
        }
        //2、否，根据id查询数据库
        Shop shop = getById(id);
        //2.1、判断是否数据库中存在
        if(shop==null){
            //写如redis
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_NULL_TTL,TimeUnit.MINUTES);
            return null;
        }
        //2.2 否 返回404
        //2.3是 写入redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),30L, TimeUnit.MINUTES);
        //3 命中，直接返回
        return shop;
    }
    public static final ExecutorService CACHE_REBUID_EXECUTOR = Executors.newFixedThreadPool(10);
    public Shop queryWithLogicalExpire(Long id){
        String key = CACHE_SHOP_KEY + id;
        // 1、从redis中查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get("key");
        // 2、判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            // 存在,直接返回
            return null;
        }
        //命中，需要将json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson,RedisData.class);
        JSONObject jsonObject = (JSONObject) redisData.getData();
        Shop shop = JSONUtil.toBean(jsonObject,Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //判断是否逻辑过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //未过期，直接返回商铺信息
            return shop;
        }
        //过期，尝试获取互斥锁
        String  lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //判断是否获取锁
        if(isLock){
            //是，开启一个独立的线程，实现重建
            CACHE_REBUID_EXECUTOR.submit(()->{
                //重建缓存
                try{
                    this.ShopSaveRedis(id,20L);
                }catch (Exception e){
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        return shop;
    }
}
